There was a lot of wasted space between the cement slab and fence where I could not put chairs without them falling through the gap.
I used Sketchup to make a cement slab and the gaps between the fence using measurements of the slab. I designed my bench so that most of the weight was on the slab, but had a pointed leg that stuck into the ground for extra support.
I didn't cover the corner section since it doesn't get used. I cut some sheet wood (garbage find) to fill the hole in.
I used a tarp as actual pond liners were much bigger or much more expensive. A $6 tarp will work, especially since all of the sharp edges were covered with expanding foam.
I added water to the liner as I adjusted it so that there were very few creases in the bottom of the liner. I then stapled it into place and cut 2x4's to frame the edges
I used a small fountain pump and played with different fountain configurations. I wanted to make it look like it was made from garden equipment (planters, etc).